This research carries out both the scientific and engineering work required to develop the Geodesic Sensor Net into a commercial product for recording the brain's electrical activity at the scalp surface. The Geodesic Sensor Net uses a geodesic tension structure comprised of elastic threads to achieve a regular tesselation of the head surface, at any spatial frequency, through a simple mechanical device. The proposed research would apply this technology, scaled to 256 channels if necessary to determine the highest spatial frequency characteristics of the human scalp event-related potential (ERP) and electroencephalogram (EEG), thereby defining the density of spatial sampling required to avoid spatial aliasing. In addition, this research quantifies the sensitivity to artifacts caused by the Net's typically high scalp impedance and the error in sensor location across repeated applications on the same head. Specific engineering research objectives include a new geodesic tension configuration that eliminates the circumferential band, a rigid external frame to use in positioning relative to skull landmarks, a tougher, more resilient elastomer to implement the tension structure, injection molded sensor pedestals, improved Ag/AgCl sensors, and an improved electrolyte sponge. A beta test program provides evaluation in external laboratories.